1. Technical Field
The present disclosure relates to a method of manufacturing a light emitting device which can be used for a display device, a luminaire, a display, a backlight light source for a liquid crystal display, and so forth.
2. Description of the Related Art
In recent years, various electronic components have been proposed and come into practical use, and higher performance is required for those components. This is also applied to the light emitting diodes and other light emitting devices. Particularly, in the fields of general lighting, on-vehicle lighting, or the like, requirements for higher performance have been increasing day by day, and further higher output, higher luminance, lower resistance, and higher reliability have been in demand. Further, while satisfying those performance requirements, operation on a commercial power supply system has also been demanded. A luminaire that uses a commercial power supply is required to comply with certain safety regulations, for example, those specified in JIS-C-8105-1. Particularly, in order to eliminate risks such as electric shock, the voltage that the light emitting device must withstand (hereinafter called the “withstand voltage”) should be increased.
Conventionally, for the material of LED packages, ceramic substrates which have a high insulation resistance have been used; particularly, for optical semiconductors, alumina-based white substrates have generally been used. On the other hand, in portions to mount LED chips (also referred to as “light emitting elements”), electrically conductive patterns are provided. For example, a noble metal such as Au or Ag may be formed on a surface in such a pattern; in the case where electrolytic plating is employed, an electrically conductive pattern to apply potential becomes necessary. The electrically conductive pattern is exposed at an end portion or a back surface of the substrate to facilitate the supply of electricity from an external power supply.
However, conventional techniques have disadvantages as illustrated below. In recent years, further higher outputs have been in demand on light emitting devices. In order to realize a high output by supplying a large amount of current, an improvement in the heat dissipating property of the light emitting devices becomes important. Accordingly, for example, an LED (also referred to as a “light emitting device”) may be mounted on a metal member which has high heat dissipating property, such as a heat sink.
For example, in JP2004-319939A, an Ag-plated layer which has a high reflectance is used for a reflecting surface, and thus obtains an improvement in the light extraction efficiency. However, in order to obtain an Ag plated surface which has a high reflectance, electrolytic plating method is needed to be used. However, in this case, the electrically conductive layer which serves as wiring for the electrolytic plating is exposed at a side surface of an insulating member, so that at the time of driving with the back surface of the insulating member brought into contact with the metal member, a short circuit due to creeping discharge may result.
Also in WO2011-099384, the surface of the electrically conductive member is covered with a reflecting member by using an electrodeposition method or electrostatic coating method, with which it is inevitable that the wiring for supplying voltage to the electrically conductive member is exposed at an end portion of the insulating member.
For this reason, in the case where a commercial power supply of an 200V system is used, the withstand voltage is required to satisfy various standards such as JIS. For example, in LEDs, the electrically conductive member located on a side surface of the substrate of the package or the like generally must be 1.5 mm or greater, more preferably 2 mm or greater, spaced apart from a metal member such as a heat sink. Accordingly, the thickness of the insulating substrate must be increased, which increases material cost and may result in a reduction of heat dissipation performance.